It’s very region specific. Just like some regions don’t have many basements, some have a lot of radon:

  Here in Maine about 36.5% of radon test results equal or exceed the Environmental Protection Agency (EPA) action level of 4 pCi/L, according to the Lung Association’s “State of Lung Cancer” report.

https://www.lung.org/media/press-releases/maine-radon-2024

If you own a basement in Maine, you should probably test it!